1. Field of the Invention
This invention relates to electro-coagulation printers that partially coagulate liquid ink by electrification to form desired images and/or characters being transferred onto printing materials such as papers.
This application is based on Patent Application No. Hei 11-290208 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Conventionally, there are provided electro-coagulation printers, an example of which is disclosed by Japanese Patent Publication No. Hei 4-504688 (which corresponds to International Publication No. WO90/11897), as follows:
The electro-coagulation printer is normally constructed by a rotation drum, plenty of electrodes and an ink supply. The electrodes are arranged to oppositely face with a circumferential surface of the rotation drum by a predetermined gap. In addition, the electrodes are aligned along an axial direction of the rotation drum with prescribed pitches therebetween. The ink supply is arranged in an incoming side of the rotation drum which is prior to proximity arrangement of the electrodes and the circumferential surface of the rotation drum being rotated in a prescribed rotation direction. The ink supply is provided to supply a film of liquid ink on the circumferential surface of the rotation drum. In printing, the plenty of electrodes are being selectively electrified. That is, electrification is performed between selected electrodes and the circumferential surface of the rotation drum with intervention of the ink. Thus, the ink is partially coagulated in response to the selected electrodes to form a desired image, which is transferred onto a printing material such as a paper.
In the electro-coagulation printer disclosed by the aforementioned publication, the liquid ink being filled in gaps between the electrodes and the circumferential surface of the rotation drum is partially subjected to coagulation by electrification wherein the electrodes are electrified in negative potentials while the circumferential surface of the rotation drum is electrified in positive potential, so that partially coagulated ink is being stuck to the circumferential surface of the rotation drum. Herein, there is a possibility in that the coagulated ink is also stuck to peripheral portions of the electrodes, which are arranged opposite to the circumferential surface of the rotation drum. In that case, the coagulated ink may be firmly attached to the peripheral portions of the electrodes, or it covers surfaces of the electrodes. This causes electrification failure (or print failure). The aforementioned publication teaches that the electrification failure can be cleared by cleaning the surfaces and peripheral portions of the electrodes with a rotation brush. However, printing should be interrupted for cleaning, which brings reduction in printing efficiency of the electro-coagulation printer.
It is an object of the invention to provide an electro-coagulation printer that prevents coagulated ink from being stuck to surfaces and peripheral portions of electrodes under electrification on a rotation drum.
It is another object of the invention to provide an electro-coagulation printer that allows easy and accurate injection of electrolyte flowing between the electrodes and liquid ink.
This invention is applicable to an electro-coagulation printer which is basically constructed by a rotation drum having a circumferential surface being electrified in positive potential, a number of electrodes being selectively electrified in negative potentials, and an ink supply device. The electrodes are aligned to oppositely face with the circumferential surface of the rotation drum with a gap which ranges between thirty and one-hundred microns, for example. The ink supply device is arranged in an incoming side of the rotation drum and supplies liquid ink to be injected onto the circumferential surface of the rotation drum, so that electrification is performed between the electrodes and circumferential surface of the rotation drum with intervention of the liquid ink. Thus, a desired image is formed on the circumferential surface of the rotation drum and is transferred onto a printing material such as a paper.
This invention contributes to improvement of the aforementioned electro-coagulation printer by introducing electrolyte for protection and cleanness of the electrodes. That is, electrolyte containing substantially no coagulating components is supplied to the electrodes to prevent the liquid ink from being stuck to surfaces and peripheral portions of the electrodes. In addition, this invention introduces an ink film thickness regulation roller which is arranged along the incoming side of the rotation drum and is located between the ink supply device and proximity arrangement of the electrodes and circumferential surface of the rotation drum. The ink film thickness regulation roller regulates the liquid ink on the circumferential surface of the rotation drum to a prescribed thickness (T1) which is smaller than the gap between the electrodes and the circumferential surface of the rotation drum. This brings a gap of a remaining thickness (T2) between the electrodes and the ink film having the prescribed thickness. Thus, the electrolyte is being introduced and drawn into the gap of the remaining thickness in contact with the electrodes. Thus, electrification is performed in such a manner that the liquid ink having the prescribed thickness is placed on the circumferential surface of the rotation drum, while the electrolyte is placed in contact with the electrodes, wherein the liquid ink and electrolyte are arranged in different phases.
In the above, the electrolyte is being output from an outlet, which is arranged between the ink film thickness regulation roller and proximity arrangement of the electrodes and circumferential surface of the rotation drum. Incidentally, it is possible to provide circulation of the electrolyte being output from the outlet.